Tracking magnetic media is becoming more difficult as trackwidths decrease to and beyond submicrometer dimensions, and the need to read and write such narrow tracks is challenging conventional systems. The inventor herein has previously developed a technique for servoing a magnetic recording head, as set forth in U.S. Patent application Ser. No. 08/100,567, filed Jul. 30, 1993, the disclosure of which is incorporated herein by reference. However, due to recent advances in the fabrication of multielement thin film transducers, the inventor has succeeded in designing a new magnetic recording head having a novel servoing technique.
The magnetic recording head of the present invention is based on the vernier approach to measurement, where a small scale rides along a larger scale and the graduations of the two scales are adjusted to improve positioning resolution. The recording head comprises multiple read transducers and multiple write transducers spaced at different intervals. The write transducers are used initially to write several servo tracks on a blank magnetic medium. Thereafter, the recording head can be successively shifted by one trackwidth each time so that the write transducers can write a first set of a multiple number of data tracks adjacent to the servo tracks. During this write operation, and as the write transducers are positioned at each of the multiple number of data track locations, one of the read transducers is always tracking one of the servo tracks to continuously position the recording head, thereby ensuring that the data tracks are accurately aligned with each other and the servo tracks.
The read transducers are positioned on the recording head such that one read transducer always tracks a servo track during each read and write operation. Thus, when the recording head is shifted by one trackwidth to write an adjacent set of data tracks, another and different read transducer will track one of the servo tracks. In this manner, the recording head can be accurately shifted in increments of a trackwidth to write several sets of data tracks, with a read transducer tracking a servo track during each write operation, until the recording head has written data tracks on all of the available medium space between the adjacent pairs of servo tracks.
As explained in greater detail below, the inventor achieves a vernier by spacing the write transducers and read transducers uniformly but at different intervals. In the preferred embodiment, the write transducers are spaced such that any two adjacent write transducers is separated by the space comprising the total number of data tracks and their associated intertrack spacing. The read transducers are spaced by a space which is one trackwidth less than the write transducer spacing. By locating one write transducer and associated read transducer at adjacent track positions, this arrangement between the read transducers and write transducers will result in associated read transducer and write transducer pairs being adjacent, one trackwidth apart, two trackwidths apart, etc. such that a pair of associated read and write transducers are required for each data track desired to be written between adjacent servo tracks. Of course, while this uniform, but unequal, spacing between write transducers and read transducers results in the desired positioning thereof, a randomized positioning which achieves the necessary transducer positions will also achieve the intended purpose of the present invention.
When the recording head has written data tracks on all the available space between adjacent servo tracks, and has therefore completed a data field, the recording head can be shifted to begin writing a new data field adjacent to the completed data field. The inventor has conceived of a couple of techniques in regard to the writing of the new data field. The recording head can simply be shifted an arbitrarily sufficient distance to ensure that the new data and servo tracks will not be written over the tracks of the completed data field. This approach will usually result in some amount of unused magnetic medium disposed between the two fields, which is more than adequate except in those applications requiring absolutely the highest data packing ratios. Alternatively, a read transducer can track one of the servo tracks of the completed data field as the servo tracks of the new data field are written. This results in closely adjacent splicing of the adjacent fields, and eliminates unused magnetic medium therebetween.
The servoing technique of the present invention has many advantages over conventional servoing techniques. The original servo pattern is written without the need for an external servo pattern writer, the data fields can be spliced, and additional read transducers that would be otherwise inactive during a particular write operation can be used to improve data recovery or servoing. With the transducer positioning of the present invention, not only is a read transducer always indexed over a servo track, but a read transducer is also immediately to the right and another is immediately to left of other servo tracks. This transducer arrangement helps ensure very accurate transducer positioning and tracking. Moreover, with additional signal processing, the servo tracks can store random data instead of servo data, thereby maximizing the useable space of the magnetic medium.